Linear peristaltic pump

ABSTRACT

An improved technique for delivering a fluid to an outlet from a storage container takes the form of a linear peristaltic pump which enables the use of two elements: a single bearing and a valve. The single bearing provides enough pressure to a flexible tube in which the fluid moves to close the tube off at a single location. The valve controls the fluid flow out of the flexible tube at the egress point in conjunction with the bearing and is attached to the flexible tube at a single location. In this manner, when the bearing is engaged with the flexible tube, the bearing divides the flexible tube into two subvolumes, one of which contains fluid to be moved toward the egress point at the far end of the flexible tube and the other creating suction for intake of fluid immediately behind the bearing. A bearing controller moves the bearing along the surface of the flexible tube when so engaged; in doing so, the bearing moves the fluid.

BACKGROUND

In semiconductor manufacturing environments, photoresist is deposited onto semiconductor wafers by a process known as spin coating. In spin coating, a deposition mechanism deposits a predetermined amount of photoresist onto the center of a wafer; a spin mechanism then spins the wafer. The spinning motion of the wafer provides an essentially uniform layer of photoresist having a precisely specified thickness. The photoresist itself, along with having an essentially uniform thickness, will also be free of contaminants.

Photoresist in such an environment needs to be delivered to an outlet in a tightly controlled manner with an almost zero tolerance for contaminants. That is, photoresist is moved from a storage container to a deposition area at a constant volumetric flow rate. Further, the medium through which the photoresist moves is not to introduce particulates.

In order to accomplish these demanding objectives, a conventional pump system designed to deliver photoresist from storage container to deposition mechanism employs a series of filters and valves.

SUMMARY

Unfortunately, such a conventional pump system as that described above suffers from deficiencies. For example, diaphragm and syringe type pump systems tend to have multiple check valves which make it difficult to control photoresist contaminant levels and add substantially to cost. Conventional rotary type, multiple element-element peristaltic pump systems, while simple, will pulsate the flow, which is undesirable.

In contrast to the above-described conventional pump system, an improved technique for delivering a fluid to an outlet from a storage container takes the form of a linear peristaltic pump which enables the use of two elements: a single bearing and a valve. The single bearing provides enough pressure to a flexible tube in which the fluid moves to close the tube off at a single location. The valve controls the fluid flow out of the flexible tube at the egress point in conjunction with the bearing and is attached to the flexible tube at a single location. In this manner, when the bearing is engaged with the flexible tube, the bearing divides the flexible tube into two subvolumes, one of which contains fluid to be moved toward the egress point at the far end of the flexible tube and the other creating suction for intake of fluid immediately behind the bearing. A bearing controller moves the bearing along the surface of the flexible tube when so engaged; in doing so, the bearing moves the fluid. When the fluid has been moved from the flexible tube, the bearing controller lifts the bearing from the flexible tube, the valve closes and the bearing controller then moves the bearing back to a starting position, and back toward the flexible tube, where the above-described process repeats itself.

One embodiment of the improved technique is a peristaltic pump device configured to move a fluid from a storage container along an interior of a flexible tube. The peristaltic pump device includes a single roller constructed and arranged to apply pressure to an outer surface of the flexible tube when fluid from the storage container is in the interior of the flexible tube. The peristaltic pump device also includes a roller controller constructed and arranged to constrain the single roller to movements (i) along the outer surface of the flexible tube, (ii) toward the outer surface of the flexible tube to provide a compression of a volume of the interior of the flexible tube, the compression sufficient to divide the volume of the interior of the flexible tube into two distinct subvolumes and (iii) away from the outer surface of the flexible tube to relieve the compression. The peristaltic pump device further includes a valve attached to the flexible tube at a single location, the valve constructed and arranged to, in conjunction with the single roller, control flow of the fluid through the interior of the flexible tube.

A further embodiment of the improved technique is a method of moving a fluid from a storage container along an interior of a flexible tube. The method includes drawing the fluid from the storage container to a near end of the flexible tube. The method also includes moving a single roller to an outer surface of the flexible tube, the moving ceasing when the single roller divides the interior of the flexible tube into two subvolumes in which fluid in each subvolume does not flow into the other subvolume. The method further includes moving the single roller along the outer surface of the flexible tube while maintaining a pressure sufficient for the interior of the flexible tube to remain divided into the two subvolumes. The method further includes operating a valve constructed and arranged to control flow of the fluid through the interior of the flexible tube to a far end of the flexible tube, the valve attached to the flexible tube at a single location.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention.

FIG. 1 is a drawing of a peristaltic pump device which operates according to the improved technique.

FIG. 2 is a schematic drawing of a photoresist delivery system which utilizes the peristaltic pump device illustrated in FIG. 1.

FIG. 3 is a flow chart which illustrates the method carried out by the improved technique.

DETAILED DESCRIPTION

An improved technique for delivering a fluid to an outlet from a storage container takes the form of a linear peristaltic pump which enables the use of two elements: a single bearing and a valve. The single bearing provides enough pressure to a flexible tube in which the fluid moves to close the tube off at a single location. The valve controls the fluid flow out of the flexible tube at the egress point in conjunction with the bearing and is attached to the flexible tube at a single location. In this manner, when the bearing is engaged with the flexible tube, the bearing divides the flexible tube into two subvolumes, one of which contains fluid to be moved toward the egress point at the far end of the flexible tube and the other creating suction for intake of fluid immediately behind the bearing. A bearing controller moves the bearing along the surface of the flexible tube when so engaged; in doing so, the bearing moves the fluid. When the fluid has been moved from the flexible tube, the bearing controller lifts the bearing from the flexible tube, the valve closes and the bearing controller then moves the bearing back to a starting position, and back toward the flexible tube, where the above-described process repeats itself.

FIG. 1 shows a peristaltic pump device 10 which is suitable for use by the improved technique. The peristaltic pump device 10 includes a flexible tube 14, a bearing 16, a motor 18, and a linkage system 20. Bearing 16 is controlled by motor 18 via linkage system 20. At one end of the flexible tube is a valve 30. At a far end of flexible tube 14 is a filter 28.

Flexible tube 14 connects, at one end, to a storage tank or source containing fluid to be moved through flexible tube 14. Flexible tube 14, if used to move photoresist, is typically about 1 foot long, with a ⅜ inch inner diameter (ID) and ⅝ inch outer diameter (OD). In such an application, flexible tube 14 is made of GORE 500, although other materials are possible.

Bearing 16 is configured to move along flexible tube 14, providing a degree of compression. Bearing 16 is a cylindrically shaped bearing having a borehole and smooth surface. The borehole in this case has a ¼ inch bore diameter and a ¾ inch outer diameter. A bearing as described here is manufactured by AST Bearings LLC, Montville, N.J.

Motor 18 is configured to control the motion of bearing 16. Motor 18 is a servo motor rated at 16,000 counts per revolution, while providing about 60 oz-in of continuous torque with which to maintain a compression on flexible tube 14 using bearing 16. A motor as described here is manufactured by Teknic, Inc. of Pittsford, N.Y.

Linkage system 20 connects the motion of motor 18 to that of bearing 16 and defines the compression that bearing 16 is able to apply to flexible tube 14. Linkage system 20 includes a pulley system 22, a ballscrew 24, and a linkage bearing 26. Motor 18 drives pulley system 22, which is connected to ballscrew 24, along which linkage bearing 26 moves.

Pulley system 22, which includes a timing belt 21 and a pair of hubs 23, links the output of motor 18 to other moving parts of the pump device 10. Timing belt 21 is a ¼-inch wide polyurethane, double-sided belt with a Kevlar tension member. Timing belt 21 further has a 0.08 inch pitch and 150 grooves. Hubs 23 are made from aluminum alloy, have a ¼ inch borehole, and are designed to fit ¼ inch timing belts. An outer hub surface also has a 0.08 inch pitch and has 36 grooves. A timing belt and pulley hub such as that described here is manufactured by SDP/SI, Inc., New Hyde Park, NY.

Ball screw 24 is connected to timing belt 21 and is configured to receive output from motor 18 through timing belt 21. Ball screw 24 is configured to convert a rotational motion [induced from timing belt 21] into a linear motion and includes a 0.5 m long shaft along which the linear motion occurs. A ball shaft such as that described here is manufactured by THK Co., LTD, Schaumberg, Ill.

Ball screw 24 also includes linkage bearing 26, which moves along ball screw 24 in the linear motion. Linkage bearing 26 is connected to bearing 16 and guides the movement of bearing 16 along flexible tube 14.

Linkage bearing 26 is further configured to move bearing 16 along a direction normal to ball screw 24. This motion ensures that bearing 16 can be moved toward and away from flexible tube 14 in order to provide an appropriate amount of pressure for compression and for relief.

Filter 28 is configured to remove contaminants from the fluid before it is sent to an outlet. Preferably, filter 28 is positioned closer to the near end of flexible tube than is valve 30. Filter 28 is rated to 0.2 microns. Filters such as those described here are manufactured by Parker Hannifin, Cleveland, Ohio.

Valve 30 is configured to control, in conjunction with bearing 16, a flow rate of the fluid through flexible tube 14. Valve 30 is a pneumatic actuated, 2-way valve rated for high pressures (up to 100 PSIG) ; at room temperatures, this translates into a flow rate of almost 18 liters/minute. Valves such as those described here are manufactured by Saint Gobain Performance Plastics—USA, Garden Grove, Calif.

During operation, bearing 16 is moved away from an outer surface of flexible tube 14. At the end of flexible tube 14 connected to a storage tank containing fluid to be. moved by peristaltic pump 10 (the near end of flexible tube 14), fluid is taken into flexible tube 14. Linkage system 20 guides bearing 16 to a start position along flexible tube 14 close to the near end. At this point, valve 30 opens. Bearing 16 then moves against the outer surface of the near end of flexible tube 14 in such a way that opposite interior surfaces of flexible tube 14 touch and there are two subvolumes within flexible tube 14. Bearing 16 then moves at a predetermined rate along the outer surface of flexible tube 14 from the near end to a far end of flexible tube 14. In this movement along the outer surface, the roller in effect squeezes, without touching, the fluid through the interior of flexible tube 14 toward the far end. Controlling fluid flow at one end of flexible tube 14 is valve 30, which can be activated pneumatically to start or stop flow of the fluid in or out of flexible tube 14 at either end. Flow rate can be limited, however, by filter 28, which removes any contaminants in the fluid before the fluid is sent to an outlet.

When bearing 16 reaches an end point along flexible tube 14, linkage system 20 lifts bearing 16 away from flexible tube 14. At this point, valve 30 closes and the operation described above repeats.

Advantageously, peristaltic pump 10 is able to deliver a larger, non-pulsating fluid flow because there is only a single valve controlling fluid flow. Because valve 30 is a pneumatically actuated valve, valve 30 is able to withstand higher pressures and can deliver the smooth flows expected in a high throughput semiconductor manufacturing environment. Further, because there are few moving parts in peristaltic pump 10, peristaltic pump 10 is less expensive, has fewer opportunities for the introduction of contaminants into the fluid and is easier to maintain.

Details of operation of peristaltic pump 10 within a semiconductor manufacturing environment are discussed below with respect to FIG. 2.

FIG. 2 shows a semiconductor manufacturing environment which utilizes peristaltic pump 10. Specifically, illustrated in FIG. 2 is a spin coat system 40 which is constructed and arranged to deliver a predetermined amount of photoresist to wafer 48 within a fixed time interval. Spin coat system 40 includes peristaltic pump 10, photoresist container 42 and photoresist delivery device 44.

Photoresist container 42 usually holds one gallon of photoresist and is placed in a position accessible to peristaltic pump 10. Flexible tube 14 of peristaltic pump 10 is connected to an opening in container 42 through which photoresist is acquired (e.g., by capillary action).

Photoresist delivery device 44 transfers photoresist from the output of peristaltic pump 10 to wafer 48. Photoresist delivery device 44 includes a nozzle 46 out of which photoresist is introduced onto the surface of wafer 48.

Flow rate and flow volumes delivered to an outlet connected to spin coat system 40 are determined by needs of the spin coat system 40, for example, the volume of photoresist needed to coat a 12 inch wafer over a 5 second period. Because motor 18 is a high resolution servo motor and the valve is pneumatically activated, the flow rate and volume is precisely controlled. Because of the fact that it is a peristaltic pump moving the fluid along the interior of flexible tube 14, contaminants within the fluid are limited, allowing a greater flow rate through filter 28 and permitting a greater throughput in coating wafers with photoresist.

When dispensing photoresist, it is desireable to ensure that there is no “final drop” in the outlet. Accordingly, before the fluid reaches the outlet, one sucks back a column of fluid within flexible tube 14. Such a suck back is accomplished by moving bearing 16 along the outer surface of flexible tube 14 toward the near end for a short distance and then closing valve 30 and lifting bearing 16 away from flexible tube 14 to return it to the start position as described above.

While various embodiments of the invention have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

For example, valve 30 can be positioned at the near end of flexible tube 30.

Further, valve 30 can be a suckback valve having suckback capability. That is, instead of reversing flow, valve 30 sucks back fluid on its far side.

Furthermore, peristaltic pump 10 can be utilized in environments other than the semiconductor processing environments discussed above. For example, peristaltic pump 10 can be configured for use in intravenous fluid delivery devices. 

1. A peristaltic pump device configured to move a fluid from a storage container along an interior of a flexible tube, the peristaltic pump device comprising: a single roller constructed and arranged to apply pressure to an outer surface of the flexible tube when fluid from the storage container is in the interior of the flexible tube; a roller controller constructed and arranged to constrain the single roller to movements (i) along the outer surface of the flexible tube, (ii) toward the outer surface of the flexible tube to provide a compression of a volume of the interior of the flexible tube, the compression sufficient to divide the volume of the interior of the flexible tube into two distinct subvolumes and (iii) away from the outer surface of the flexible tube to relieve the compression; and a valve attached to the flexible tube at a single location, the valve constructed and arranged to, in conjunction with the single roller, control flow of the fluid through the interior of the flexible tube.
 2. A peristaltic pump device as in claim 1, wherein the flexible tube has a near end and a far end, the near end of the flexible tube attached to the storage container; wherein the valve is located in the vicinity of the far end of the flexible tube; and wherein the motion of the roller controller along the outer surface of the flexible tube is constructed and arranged to, in conjunction with the valve, deliver a predetermined volume of the fluid to a fluid delivery device at a predetermined rate.
 3. A peristaltic pump device as in claim 1, wherein the flexible tube has a near end and a far end, the near end of the flexible tube attached to the storage container; wherein the valve is located in the vicinity of the near end of the flexible tube; and wherein the motion of the roller controller along the outer surface of the flexible tube is constructed and arranged to, in conjunction with the valve, take in a predetermined volume of the fluid to the interior of the flexible tube.
 4. A peristaltic pump device as in claim 2, wherein the fluid is a photoresist; and wherein the far end of the flexible tube connects to a spin-coat device through which the photoresist is delivered to a substrate as a substantially flat layer on the substrate.
 5. A peristaltic pump device as in claim 2, wherein the roller controller includes: a servo motor which includes an output shaft, the servo motor being constructed and arranged to move the output shaft at a substantially constant angular velocity; and a linkage system which connects the movement of the output shaft to that of the single roller.
 6. A peristaltic pump device as in claim 2, further comprising: a bubble catcher attached to the far end of the flexible tube, the bubble filter being constructed and arranged to remove air bubbles from the fluid.
 7. A peristaltic pump device as in claim 2, wherein the valve has a near end and a far end, the far end pointing away from the flexible tube; and wherein the valve provides suckback capability on its far end.
 8. A method of moving a fluid from a storage container along an interior of a flexible tube, the method comprising: drawing the fluid from the storage container to a near end of the flexible tube; moving a single roller to an outer surface of the flexible tube, the moving ceasing when the single roller divides the interior of the flexible tube into two distinct subvolumes; moving the single roller along the outer surface of the flexible tube while maintaining a pressure sufficient for the interior of the flexible tube to remain divided into the two subvolumes; and operating a valve constructed and arranged to control flow of the fluid through the interior of the flexible tube to a far end of the flexible tube, the valve attached to the flexible tube at a single location.
 9. A method as in claim 8, wherein the valve is located in the vicinity of the far end of the flexible tube; and wherein moving the single roller along the outer surface of the flexible tube comprises: delivering, in conjunction with the valve, a predetermined volume of the fluid to a fluid delivery device at a predetermined rate.
 10. A method as in claim 8, wherein the valve is located in the vicinity of the near end of the flexible tube; and wherein moving the single roller along the outer surface of the flexible tube comprises: delivering, in conjunction with the valve, a predetermined volume of the fluid to the interior of the flexible tube.
 11. A method as in claim 9, wherein the fluid is a photoresist; and wherein moving the single roller along the outer surface of the flexible tube further comprises: delivering, through a spin-coat device connected to the far end of the flexible tube, the photoresist to a substrate as a substantially flat layer on the substrate.
 12. A method as in claim 9, wherein moving the single roller along the outer surface of the flexible tube further comprises: moving an output shaft of a servo motor at a substantially constant angular velocity, the output shaft being connected to a linkage system which connects the movement of the output shaft to that of the single roller.
 13. A method as in claim 9, further comprising: removing air bubbles from the fluid.
 14. A method as in claim 9, wherein the valve has a near end and a far end, the far end pointing away from the flexible tube; and wherein the method further comprises: providing suckback capability at the far end of the valve. 